JPS62101666A - Paint resin composition - Google Patents

Abstract

PURPOSE:To provide a paint resin compsn. which is suitable for use in coating automobiles and gives a coating film which hardly causes weight reduction on heating and loss by scattering during baking, by blending an alkyl-etherified amino resin having specified properties, obtd. by a specified manufacturing process, with a resin capable of being cured by the reaction with said resin. CONSTITUTION:Melamine or benzoguanamine and formaldehyde are subjected to an addition reaction and then a condensation reaction at a relatively strong acidity and further an etherification reaction with an alcohol (e.g., n-butanol) is carried out. In this way, an alkyl-etherified amino resin wherein the proportion of each of moieties having one triazine nucleus and two triazine nucleuses in the molecule is 10wt% or below and the content of free formaldehyde is 1.5wt% or below can be obtd. Said amino resin is blended with a resin capable of being cured by the reaction with said amino resin (e.g., an acrylic resin, an alkyd resin), a pigment, etc., to obtain the desired paint resin compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a resin composition for paint containing an alkyl etherified amino resin.

[Conventional technology]

BACKGROUND ART Thermosetting resin compositions made by combining alkyl etherified amino resins with alkyd resins, acrylic resins, epoxy resins, etc. have been used for paints. Recently, there has been a strong demand for labor-saving, resource-saving, energy-saving, etc., and work rationalization for coating paints for automobiles, industrial machinery, steel furniture, electrical appliances, buildings, etc.

To solve these problems, it is desirable to be able to cure at a low temperature of 90 to 110C x 20 minutes, or to be able to bake for a short time at a high temperature such as 200 to 2500C.

In conventional aminoalkyd resins or aminoalkyd resins, the alkyl etherified aminobun resin used has a relatively small number average molecular weight and contains a relatively large amount of bound formaldehyde and butyl ether groups in the resin, and the molecule It is a mixture of substances having one to several dozen triazine nuclei within the molecule, and the proportion of substances having one triazine nucleus within the molecule is 15 to 20% by weight.

[Problem that the invention seeks to solve]

Paints using such resins volatilize low-molecular parts together with organic solvents during the curing reaction, and may adhere to the inside of the drying oven or coagulate and solidify when they come into contact with low-temperature atmospheres such as the entrance and exit of the oven, dust inner walls, and duct leaks. I will do it. These scattered substances may fall onto the objects to be coated at the entrance/exit of the furnace, resulting in product defects, ignition of deposits, etc., and cleaning may cause problems such as an increase in cleaning management costs when managing the furnace. .

[Means for solving problems]

The present invention is characterized in that: (1) melamine or benzoguanamine is obtained by etherification reaction with formaldehyde, added Zr, and alcohol, and the proportions of those having one and two triazine nuclei in the molecule are respectively 10 M% or less, The present invention relates to a resin composition for a coating material, which contains an alkyl etherified amino resin having a content of 1.5% by weight or less, and CB) a resin that can be cured by reacting with the alkyl etherified amino resin.

The alkyl etherified amino resin which is component (A) of the present invention uses melamine or benzoguanamine as an amino compound as a raw material, and the proportion of one and two triazine nuclei in the molecule is 10% by weight or less, respectively. If the amount of the material having one or two triazine nuclei in the molecule exceeds 10% by weight, a large amount of low-molecular substances will volatilize during heat curing, and a large proportion will adhere to the inside of the drying oven. Furthermore, if the content of unreacted melamine, benzoguanamine, or formaldehyde-poor adducts of melamine and benzoguanamine is high, the rate of volatilization and adhesion increases. Furthermore, free formaldehyde also has an adverse effect. In other words, as stated in the April 1981 issue of Paint Technology, formaldehyde is said to have an effect of accelerating the reductive decomposition of substances that volatilize and adhere to it, thereby increasing the amount of formaldehyde generated. Conventional melamine resins or benzoguanamine resins with a weight of 1.5% or less are also commercially available, but the molecular weight of these resins is 10% by weight, which contains one or two triazine nuclei in the molecule. In addition, there is a drawback to the durability of these coaters.Another drawback is that the product price is high due to the composition.

It can be produced by addition reaction with formaldehyde in alcohol, followed by condensation reaction and alkyl etherification at relatively strong acidity. Preferably, after this, an alcohol such as butanol is further added and heated to reduce the viscosity. Finally, the solvent may be removed to reach the desired solid content. In the above reactions, excluding the addition reaction step, hydrochloric acid, sulfuric acid, phosphoric acid, para-toluenesulfonic acid, and phthalic acid.

It is preferable to add an acidic catalyst such as uric acid or formic acid to carry out the reaction in an acidic environment (preferably pH 3 to 4.5). The reaction temperature is preferably the reflux temperature of alcohol, and in the case of butanol, for example, it is preferably 90 to 120C.

For example, it is preferable to use 4 to 7 moles of cyformaldehyde and 4 to 8 moles of U-fluorol per mole of melamine, and 1.8 to 30 moles of formaldehyde and 2 to 4 moles of alcohol per mole of benzoguanamine.
It is preferable to use moles.

The molecular weight distribution of the alkyl etherified amino resin thus obtained can be measured by gel permeation chromatography, and the proportion of those having one or two triazine nuclei in one molecule can be determined by the cutout weight method. .

The main component of the alkyl etherified amino resin of the present invention is one having 3 to 10 triazine nuclei in the molecule, and n
- Viscosity when dissolved in a mixed solvent of 1/1 butanol/xylene (weight ratio) to a solid content of 60% by weight (
As the resin that can be cured by reacting with Gardner, 25C) formaldehyde resin, conventionally known resins such as acrylic resin, alkyd resin, and alkyd resin-modified acrylic resin can be used. These preferably have a hydroxyl value of 15 to 200 in order to react with the butyl etherified melamine/formaldehyde resin.

The alkyd resin is a resin obtained by reacting, for example, a polyhydric carboxylic acid, a polyhydric alcohol, and, if necessary, oil or fat or a fatty acid thereof. Phthalic acid and isophthalic acid are polyhydric carboxylic acids.

These include terephthalic acid, tetrahydrophthalic acid, maleic acid, fumaric acid, succinic acid, adipic acid, sepanoic acid, trimellitic acid, and pyromellitic acid.

These may be used in the form of ester-forming derivatives such as acid anhydrides and methyl esters. Polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, glopylene glycol, dipropylene glycol, neopentyl glycol, 1.4-butanediol, 1.6-hexaneol, 1-! of,'
Tylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol natcal.

Examples of the oil include tung oil, linseed oil, soybean oil, dehydrated castor oil, safflower oil, castor oil, coconut oil, and tall oil. The alkyd resin can be produced by a known method, and when oil is used, oil and polyhydric alcohol are reacted at 200 to 260 C in the presence of a transesterification catalyst such as lithium hydroxide, and then a polybasic acid , a method of adding the remaining polyhydric alcohol and reacting at 180 to 250C, and a method of mixing raw materials and reacting at 180 to 250C when no oil is used.

Acrylic resins include 2-hydroquinoethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl acrylate.
It is obtained by copolymerizing α,β-ethylenically unoriented saturated monomers having 7 hydroxy groups such as -hydroquinoethyl and 2-hydroxypropyl methacrylate, and other unsaturated monomers. Other unsaturated monomers include
α, β-monoethylenically unoriented saturated carboxylic acids such as acrylic acid, methacrylic acid, maleinoic acid, itaconoic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate,
2-ethylhexyl acrylate, methyl methacrylate,
α,β-monoethylenically unsaturated carboxylic acid alkyl ester such as n-butyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide,
Acrylamide derivatives such as N-methylolmethacrylamide and diacetone acrylamide, α,β-monoethylenically unoriented saturated carboxylic acid lysine esters such as glinosyl acrylate and glycidyl methacrylate, and saturated carboxylic acids such as vinyl acetate and vinyl propionate. Examples include aromatic unsaturated monomers such as vinyl ester, styrene, α-methylstyrene, and vinyltoluene. The above copolymerization is carried out in the presence of a radical catalyst such as azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, or cumene hydroperoxide.
This can be done by heating to 0C.

The alkyd resin-modified acrylic resin can be obtained by polymerizing monomers that are raw materials for the acrylic resin in the presence of the alkyd resin.

The raw material composition of the alkyd resin, acrylic resin, and alkyd resin-modified acrylic resin is preferably adjusted so that the hydroxyl value is 15 to 200. Note that if the hydroxyl value is too small, the curability will be poor, and if it is too large, the water resistance of the coating film will be poor.

In the present invention, the butyl etherified melamine/formaldehyde resin and the resin capable of reacting with the resin and curing the resin are preferably blended so that the weight ratio of the former to the latter is IQ/90 to 70/30.

If it is less than 10/90, curing performance tends to be poor;
If it exceeds /30, the flexibility of the coating film tends to be poor.

The thermosetting resin composition according to the present invention includes hydrochloric acid, phosphoric acid,
A catalyst such as para-toluenesulfonic acid may also be added. The amount used is preferably 1% by weight or less based on the butyl etherified melamine/formaldehyde resin.

Furthermore, the thermosetting resin composition according to the present invention includes xylene,
Toluene, butyl cellosolve, ethyl cellosolve, n-
It is used by adjusting the solid content to an appropriate level using organic solvents such as butanol, isobutanol, impropatol, and methanol.

Depending on the purpose, pigments such as titanium white and other additives may be added to the thermosetting resin composition according to the present invention.

Further, as a coating method, spray painting, dipping, etc. can be adopted.

〔Example〕

Next, production examples and examples related to the present invention will be shown.

Hereinafter, parts and % indicate parts by weight and % by weight, respectively.

Artificial Example 1 Weighed 126 g of melami, 444 g of n-butanol, and 187.5 g of paraformaldehyde into a flask equipped with a stirrer, a reflux condenser, and a thermometer. The addition reaction was carried out for 1 hour. Then, adjust the pH to 5-6.5 with nitric acid.
The mixture was heated again and dehydrated for 3 hours under reflux. Thereafter, desolvation was started at the same temperature (reflux was stopped), and when the temperature of the contents of the flask reached 130C, the desolvation was terminated. After this, the heating residue was adjusted to 60%. Viscosity at this time (Gardner, 2SC
) was Z+. Thereafter, the mixture was further heated under reflux at 90C for 2 hours, and then the reflux was stopped to remove the solvent. The end point of the solvent removal was when the temperature of the contents of the flask reached 125C. The heating residue of the resin solution obtained at this time was 80%. In addition, the composition of the solvent is xylene/n-
Xylene and n-butanol were added so that the butanol content was 1/1 (weight ratio) and the heating residue was 60%. The viscosity (Gardner, 25C) of the obtained butyl etherified amino resin solution was Y.

Artificial example 2 93.5 g of benzoguanamine, 763 g of melami.

333 g of n-butanol and 13 g of paraformaldehyde
1.25 g was charged into a flask similar to that used in Production Example 1, and addition reaction was carried out at 90C for 1 hour.

Then, the pH was adjusted to 4 to 6 with nitric acid, heated again, and dehydrated for 2 hours under reflux. After that, 74g of n-butanol was added and dehydration was performed for 1 hour under reflux.
Subsequently, the reflux was stopped and the solvent was removed, and when the temperature of the contents of the flask reached 135C, the removal of the solvent was stopped. Thereafter, in the same manner as in Production Example 1, an n-butyl etherified amino resin solution with a heating residue of 60% was obtained. The viscosity of this (Gardner, 25t?) was 2.

Production Example 3 The same procedure as Production Example 1 was carried out using 187 g of benzoguanamine, 185 g of n-butanol, and 93.75 g of paraformaldehyde. However, nitric acid reduces p f-I to 4~
6, and the end point of the first desolvation was 135C and the end point of the second desolvation was 120C. The obtained n-
Viscosity of butyl etherified amino resin solution (Gardner,
2Sc) was X.

Comparative Production Example 1 Using the same apparatus as in Production Example 1, 126 g of melamine and 444 g of paraformaldehyde and 225 g of paraformaldehyde were weighed and subjected to an addition reaction of 90C for 1 hour. After that, the temperature was adjusted to I) H5-6 with nitric acid, heated again, and dehydrated under reflux for 2 hours.
I did it for an hour. Next.

Stop the reflux and remove the solvent until the temperature of the flask contents reaches 125.
When the temperature reached C, it was determined as the end point of solvent removal. Then, in the same manner as in Production Example 1, the heating residue was adjusted to 60%. The viscosity of the resin solution at this time (Gardner).

25C) was K.

Comparative Production Example 2 The same procedure as Comparative Production Example 1 was carried out using 187 g of benzoguanamine, 185 g of n-butanol, and 93.75 g of paraformaldehyde. However, the end point of the solvent removal was set at the time when the temperature of the contents of the flask reached 130C. The viscosity of the obtained resin solution (Gardner, 25t?) was H.

Regarding the alkyl etherified amino resins obtained in Production Examples 1 to 3 and Production Comparative Examples 1 to 2, the proportions and molecular weights of those having one and two triazine nuclei in the molecule are shown in Table 1. These were determined using standard polystyrene calibration curves under the following measurement conditions: Nyorkel Vermie Neuon chromatography.

Measurement conditions Column: Hitachi Chemical Co., Ltd. product name, Gel Pack (Qe
lpack) R-420, R-430, 几-440,3
Solvent: Tetrahydrofuran Flow rate: 1.77 mt/min Temperature: 40C Sample concentration: 60 omg,/5mt Injection amount: 2
Detector: Differential refractometer Example 1 50 parts by weight of the butyl etherified melamine resin solution of Production Example 1 and alkyd resin (Hitachi Chemical Co., Ltd. trade name,
Phthalkid 804-7OA, solid content hydroxyl value 80.
Weigh out 40 parts by weight (solid content 70%) and add 100 parts by weight.
15.5g of was added to adjust the coating solid content to 55%. Apply this paint to a tin plate (10Cr11x10cm)
After measuring the weight, it was coated with a bar coater≠60. This tin plate was dried at 108C for 30 minutes, and after cooling, the weight of the membrane plate was measured.

After that, heat at 150C for 20 minutes, then heat at 180υ for 10 minutes.

Baking was carried out separately at 200C for 3 minutes and at 200C for 10 minutes, and after cooling, the weight was measured again. For heating loss, the same test was conducted five times and the average value was determined. The results are shown in Table 3. In addition, the heating loss was calculated|required according to the following formula.

Examples 2-3. Comparative Example 1-2 The weight loss on heating was determined in the same manner as in Example 1 using the formulations shown in Table 2. The results are shown in Table 3. .

Table 3 Results of measurement of loss on heating [Effects of the invention] The resin composition for paint according to the present invention has a small loss on heating during baking of a coating film, and there are few scattered substances.

Claims (1)

[Scope of Claims] 1. (A) Melamine or benzoguanamine obtained by addition condensation with formaldehyde and etherification reaction with alcohol, the proportion of which has one and two triazine nuclei in the molecule is 10% by weight or less, respectively. A resin composition for a coating material, comprising: an alkyl etherified amino resin having a free formaldehyde content of 1.5% by weight or less; and (B) a resin that can be cured by reacting with the alkyl etherified amino resin.